Pilot testing of two biofungicide formulations for the control of citrus blue and green mold in two Moroccan packinghouses

Pichia guilliermondii strain Z1 and Bacillus subtilis strain ZH2 were previously selected for their high and reliable antagonistic activities against Penicillium digitatum (Sacc.) and blue mould (P. italicum Weh.) on citrus fruits. The effectiveness of pilot testing of wettable and a granular powder formulation based on each biocontrol agent was evaluated and compared to thiabendazole in two packinghouses. Each fruit was wounded on the outer surface on two opposite locations. Fruits intended to be treated with biofungicides were recovered just before applying the wax at packaging line. Fruits were soaked in a solution made with each formulation. Pathogenic inoculation was made 24 hours later by spraying two different varieties of fruits, Clementine ‘Nules’ and ‘Valencia-late’ orange, with a suspension of 105 conidia/ml of P. italicum or P. digitatum. The effect of treatment was evaluated after 7 days of fruit incubation at two temperatures 4 °C and 20 °C. The result showed that the control achieved with strain Z1 on ‘Valencia late’ orange was comparable to that with thiabendazole. On the other hand, the decay control was lower for all the treatments on the Clementine ‘Nules’. Nevertheless, ZH2 strain has no effect at 4 °C. Therefore, it was concluded that strain Z1 is a promising biocontrol agent for the control of major postharvest diseases of citrus in Moroccan packinghouse stations. Keywords: Citrus, biological control, formulation, packinghouse, Pichia guilliermondii, Bacillus subtili

Induced Systemic Resistance (ISR) in Arabidopsis thaliana by Bacillus amyloliquefaciens and Trichoderma harzianum Used as Seed Treatments

International audienceThe Trichoderma fungal species and the bacteria Bacillus species were described as inducers of plant systemic resistance in relation to their antagonistic activity. The objective of this study was to evaluate the effect of selected strains of Bacillus amyloliquefaciens (I3) and Trichoderma harzianum (A) on inducing systemic resistance in Arabidopsis thaliana as a model for plant molecular genetics. The microorganisms were identified and were confirmed for their antagonistic potential in vitro and in vivo in previous studies. In order to explore this mechanism, two mutants of A. thaliana carrying a PR1 promoter (a conventional marker of salicylic acid (SA) pathway) and LOX2 promoter (a marker triggering jasmonic acid (JA) pathway activation) were analyzed after inoculating antagonists. Transgenic reporter line analysis demonstrated that B. amyloliquefaciens I3 and T. harzianum A induce A. thaliana defense pathways by activating SA and JA at a high level compared to lines treated with chemical elicitors of references (acibenzolar-S-methyl (Bion 50 WG (water-dispersible granule)), SA, and methyl jasmonate). The efficacy of B. amyloliquefaciens I3 and T. harzianum A in inducing the defense mechanism in A. thaliana was demonstrated in this study

Antifungal activity of bioactive compounds produced by the endophyte Bacillus velezensis NC318 against the soil borne pathogen Sclerotium rolfsii Sacc

In a previous study, the endophytic Bacillus velezensis NC318 was isolated from the rhizosphere of date palm and showed strong antifungal activity against the soil-borne plant pathogenic fungus, Sclerotium rolfsii Sacc, the causal agent of Southern blight. The potential of the Bacillus genus in the inhibition of plant pathogens is mainly due to the production of certain bioactive compounds. In the present study, secondary metabolites extracted from the cell-free supernatant of strain NC318 showed strong antifungal activity on the mycelial growth and germination of S. rolfsii sclerotia in vitro. With 50 μl of bioactive compounds crude extracts, the mycelial growth inhibition rate was 97% and any germination of sclerotia was reported. Chemical analysis of the secondary metabolite crude extracts performed by high performance liquid chromatography coupled with mass spectrometry (HPLC/MS), revealed that the secreted bioactive compounds belonged to the family of lipopeptides (iturin, fengycin, surfactin), polyketides (bacillaene, macrolactin, difficidin and bacilysin) and siderophores (bacillibactin). These results provide a better understanding of the biocontrol mechanism of the bacteria strain B. velezensis NC318 against the soil fungal pathogens, especially S. rolfsii root rot

Complete mitochondrial genome and phylogeny of the causal agent of Bayoud disease on date palm, Fusarium oxysporum f. sp. albedinis

The complete mitogenome of Fusarium oxysporum f. sp. albedinis (FOA), the causal agent of the destructive fusarium wilt in date palm, is sequenced and assembled. The circular mitogenome of isolate Foa44 is 51,601 bp in length and contains 26 transfer RNA (tRNA) genes, one ribosomal RNA (rRNA), and 28 protein-coding genes. A mitogenome-based phylogenetic analysis of Fusarium revealed that FOA is congruent with previous nuclear-gene phylogenetic results

The ability of the antagonist yeast Pichia guilliermondii strain Z1 to suppress green mould infection in citrus fruit

In previous studies it was shown that <em>Pichia guilliermondii</em> strain Z1, isolated from healthy Moroccan citrus Valencia-Late oranges, was effective against <em>Penicillium italicum</em>. Here the effectiveness of strain Z1 was assessed against <em>Penicillium digitatum</em>, the causal agent of green mould, under different temperature (5-25°C) and relative humidity (RH) (45-100%) regimes for its reliable and largescale application in packinghouse. All main effects and interactions were significant (P80%. Its applications as a formulated product significantly reduced the incidence of infected fruit (55%) and the percentage of infected wounds (47%) compared to the only pathogen control treatment. However, disease control with formulated product was significantly less than that obtained with thiabendazole (30%) or strain Z1 culturable cells (35%). These results highlight that strain Z1 is an effective biological control agent for control of green mould under varying environmental conditions, and control may be optimized by combining its use with other environmentally-safe post-harvest treatments or improved formulation

Variability and genetic structure of a natural population of <em>Citrus psorosis virus</em>

International audienceIn this study, we examined the population structure and genetic diversity of Citrus psorosis virus (CPsV) in Morocco. Analysis of the coat protein partial sequences of 34 isolates collected in the three main citrus-growing areas of Morocco showed that CPsV grouped in three major groups, with low within-group nucleotide diversity. Analyses indicated that CPsV genetic diversity is not structured by the geographic origin of the CPsV isolates. The genetic variation resulting from mutations depends on evolutionary forces that have contributed to the shaping of the genetic structure and diversity of the CPsV populations analyzed here: negative selective pressure for amino acid variation, recombination between variants or mixed infection, genetic drift induced by the founder effect associated with the transmission process, and migration explained by the exchange of infected propagative plant material

Phosphate-Solubilizing Bacteria Isolated from Phosphate Solid Sludge and Their Ability to Solubilize Three Inorganic Phosphate Forms: Calcium, Iron, and Aluminum Phosphates

Biofertilizers are a key component of organic agriculture. Bacterial biofertilizers enhance plant growth through a variety of mechanisms, including soil compound mobilization and phosphate solubilizing bacteria (PSB), which convert insoluble phosphorus to plant-available forms. This specificity of PSB allows them to be used as biofertilizers in order to increase P availability, which is an immobile element in the soil. The objective of our study is to assess the capacity of PSB strains isolated from phosphate solid sludge to solubilize three forms of inorganic phosphates: tricalcium phosphate (Ca3(PO4)2), aluminum phosphate (AlPO4), and iron phosphate (FePO4), in order to select efficient solubilization strains and use them as biofertilizers in any type of soil, either acidic or calcareous soil. Nine strains were selected and they were evaluated for their ability to dissolve phosphate in the National Botanical Research Institute’s Phosphate (NBRIP) medium with each form of phosphate (Ca3(PO4)2, AlPO4, and FePO4) as the sole source of phosphorus. The phosphate solubilizing activity was assessed by the vanadate-molybdate method. All the strains tested showed significantly (p ≤ 0.05) the ability to solubilize the three different forms of phosphates, with a variation between strains, and all strains solubilized Ca3(PO4)2 more than FePO4 and AlPO4

Efficacy of Secondary Metabolites Produced by Bacillus Amyloliquefaciens on the Inhibition of Zymoseptoria Tritici

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Elevating Sorghum Prosperity: Unveiling Growth Trends through Phosphate-Solubilizing Bacteria and Arbuscular Mycorrhizal Fungi Inoculation in Phosphate-Enriched Substrates

This study aimed to elucidate the impact of phosphate-solubilizing bacteria (PSB) and arbuscular mycorrhizal fungi (AMF) inoculation on sorghum growth within substrates derived from phosphate solid sludge, with the overarching objective of repurposing phosphate sludge to be a viable agricultural substrate. Four PSB strains (Serratia rubidaea, Enterobacter bugandensis, Pantoea agglomerans, Pseudomonas sp.) were meticulously selected from phosphate solid sludge, along with two AMF strains (Rhizophagus intraradices and Funneliformis mosseae), constituting the experimental inocula. Phosphate solid sludge was judiciously blended with peat at varying volumetric proportions (0%, 10%, 20%, 40%, and 60%), providing the matrix for sorghum cultivation, and concomitantly subjected to inoculation with PSB and AMF. Following a meticulously monitored two-month duration, a comprehensive evaluation of diverse morphological parameters, biomass accrual, nitrogen content, total phosphorus concentration, potassium levels, calcium content, and root colonization in sorghum plants was conducted. The empirical findings underscored a discernible decline in the assessed parameters with escalating concentrations of phosphate solid sludge. Particularly noteworthy was the pronounced amelioration observed in plants inoculated with AMF in comparison to both the control and PSB-inoculated counterparts. In conclusion, the application of raw phosphate solid sludge as an agricultural substrate is deemed unsuitable, prompting the imperative need for further in-depth investigations to ascertain the nuanced intricacies underlying these outcomes